Distributed snapshot policy schedule

Abstract

A method for creating snapshots is disclosed. The method includes collecting a first resource usage metric of a first storage system and a second resource usage metric for one or more second storage systems, detecting a command to create a snapshot of a storage entity, and detecting when the snapshot would be a base snapshot. When the snapshot is going to be a base snapshot, a selection policy is evaluated to identify the location where the snapshot is going to be created after which the snapshot is created at the identified location. When the snapshot would not be a base snapshot, the snapshot is stored at a location where snapshots of the storage entity are already being created.

1 . A method, comprising:
 collecting, by a distributed snapshot policy (DSP) agent that is executed in a first storage system, a first resource usage metric of the first storage system, the first storage system being configured to store a copy of a storage entity, the storage entity being a volume or a storage group, the first resource usage metric including a measure of writes pending at the first storage system;   receiving, by the DSP agent, a respective second resource usage metric for each of one or more second storage systems, each of the second storage systems also being configured to store a copy of the storage entity, each respective second resource usage metric including a measure of writes pending at a different one of the second storage systems;   detecting, by the DSP agent, that a given snapshot of the storage entity needs to be created;   detecting, by the DSP agent, whether the given snapshot would be a base snapshot;   selecting, by the DSP agent, one of the first and second storage systems as a location where the given snapshot should be created, the location being selected based on whether the given snapshot would be a base snapshot, such that: (i) when the given snapshot would be a base snapshot, the location is selected by evaluating a policy rule based on the first and second resource usage metrics, and (ii) when the given snapshot would not be a base snapshot, the location is selected by identifying the location where snapshots of the storage entity are already being created, without evaluating the policy rule; and   generating the given snapshot by one of the first storage system and the second storage systems that is selected as the location where the given snapshot should be created,   wherein the policy rule is arranged to balance a load associated with snapshot creation between the first storage system and the second storage system, the balancing being based on the first resource usage metric, any of the second resource usage metrices, and respective amounts of resources that are dedicated by each of the first and second storage systems to the creation and storage of snapshots.   
     
     
         2 . The method of  claim 1 , wherein the policy rule provides that the given snapshot should be created by one of the first and second storage systems which currently dedicates the least storage space to the storage of snapshots and/or snapshot metadata, provided that the writes pending at the storage system is less than a threshold. 
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 1 , wherein the given snapshot would be a base snapshot when the given snapshot is a first snapshot in a sequence of snapshots. 
     
     
         5 . The method of  claim 1 , wherein the given snapshot would be a base snapshot when none of the first and second storage systems has commenced taking snapshots of the storage entity. 
     
     
         6 - 7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein the identifying of the location where snapshots of the storage entity are already being created is performed based on a data structure, the data structure identifying a plurality of storage entities that have copies stored in each of the first and second storage systems, for each one of the plurality of storage entities, the data structure identifying a respective one of the first and second storage systems as a storage system where snapshots of the storage entity are being created. 
     
     
         9 . A computing device, comprising:
 a memory; and   at least one processor that is operatively coupled to the memory, the at least one processor being configured to perform the operations of:   collecting, by a distributed snapshot policy (DSP) agent, a first resource usage metric of a first storage system, the first storage system being configured to store a copy of a storage entity, the storage entity being a volume or a storage group, the first resource usage metric including a measure of writes pending at the first storage system;   receiving, by the DSP agent, a respective second resource usage metric for each of one or more second storage systems, each of the second storage systems also being configured to store a copy of the storage entity, each respective second resource usage metric including a measure of writes pending at a different one of the second of the second storage systems;   detecting, by the DSP agent, that a given snapshot of the storage entity needs to be created;   detecting, by the DSP agent, whether the given snapshot would be a base snapshot;   selecting, by the DSP agent, one of the first and second storage systems as a location where the given snapshot should be created, the location being selected based on whether the given snapshot would be a base snapshot, such that: (i) when the given snapshot would be a base snapshot, the location is selected by evaluating a policy rule based on the first and second resource usage metrics, and (ii) when the given snapshot would not be a base snapshot, the location is selected by identifying the location where snapshots of the storage entity are already being created, without evaluating the policy rule; and   causing, by the DSP agent, the given snapshot to be created at one of the first storage system and the second storage system that is selected as the location where the given snapshot should be created,   wherein the policy rule is arranged to balance a load associated with snapshot creation between the first storage system and the second storage system, the balancing being based on the first resource usage metric, the second resource usage metric, and respective amounts of resources that are dedicated by each of the first and second storage systems to the creation and storage of snapshots.   
     
     
         10 . The computing device of  claim 9 , wherein the policy rule provides that the given snapshot should be created by one of the first and second storage systems which currently dedicates the least storage space to the storage of snapshots and/or snapshot metadata, provided that the writes pending at the storage system is less than a threshold. 
     
     
         11 . (canceled) 
     
     
         12 . The computing device of  claim 9 , wherein the given snapshot would be a base snapshot when the given snapshot is a first snapshot in a sequence of snapshots. 
     
     
         13 . The computing device of  claim 9 , wherein the given snapshot would be a base snapshot when none of the first and second storage systems has commenced taking snapshots of the storage entity. 
     
     
         14 - 15 . (canceled) 
     
     
         16 . The computing device of  claim 9 , wherein the identifying of the location where snapshots of the storage entity are already being created is performed based on a data structure, the data structure identifying a plurality of storage entities that have copies stored in each of the first and second storage systems, for each one of the plurality of storage entities, the data structure identifying a respective one of the first and second storage systems as a storage system where snapshots of the storage entity are being created. 
     
     
         17 . A non-transitory computer-readable medium storing one or more processor-executable instructions, which, when executed by at least one processor, cause the at least one processor to perform the operations of:
 collecting, by a distributed snapshot policy (DSP) agent, a first resource usage metric of a first storage system, the first storage system being configured to store a copy of a storage entity, the storage entity being a volume or a storage group, the first resource usage metric including a measure of writes pending at the first storage system;   receiving, by the DSP agent, a respective second resource usage metric for each of one or more second storage systems, each of the second storage systems also being configured to store a copy of the storage entity, each respective second resource usage metric including a measure of writes pending at a different one of the second storage systems;   detecting, by the DSP agent, that a given snapshot of the storage entity needs to be created;   detecting, by the DSP agent, whether the given snapshot would be a base snapshot;   selecting, by the DSP agent, one of the first and second storage systems as a location where the given snapshot should be created, the location being selected based on whether the given snapshot would be a base snapshot, such that: (i) when the given snapshot would be a base snapshot, the location is selected by evaluating a policy rule based on the first and second resource usage metrics, and (ii) when the given snapshot would not be a base snapshot, the location is selected by identifying the location where snapshots of the storage entity are already being created, without evaluating the policy rule; and   causing the given snapshot to be created at one of the first storage system and the second storage system that is selected as the location where the given snapshot should be created,   wherein the DSP agent is executed in the first storage system wherein and the policy rule is arranged to balance a load associated with snapshot creation between the first storage system and the second storage systems, the balancing being based on the first resource usage metric, the second resource usage metric, and respective amounts of resources that are dedicated by each of the first and second storage systems to the creation and storage of snapshots.   
     
     
         18 . The non-transitory computer-readable medium of  claim 17 , wherein the policy rule provides that the given snapshot should be created by one of the first and second storage systems which currently dedicates the least storage space to the storage of snapshots and/or snapshot metadata, provided that the writes pending at that storage system is less than a threshold. 
     
     
         19 - 20 . (canceled) 
     
     
         21 . The method of  claim 1 , wherein selecting, by the DSP agent, one of the first and second storage systems as the location where the given snapshot should be created includes:
 when the first storage system is selected, updating a snapshot location data structure, by the first storage system, to indicate that the first storage system is tasked with creating snapshots of the storage entity, and   when any given one of the second storage systems is selected, transmitting from the first storage system to the given second storage system an instruction to create the given snapshot, and updating a snapshot location data structure, by the given second storage system, to indicate that the first storage system is tasked with creating snapshots of the storage entity.